Meanwhile, Slide has gone through — by our count — five business model overhauls.

In 2005, the company began as a desktop-based, photo-oriented shopping search engine. Max built it for his wife, so she could shop for shoes faster.

“The idea was to encourage her to spend more time with me and less time browsing for shoes,” Max told CNET that year.

The plan was to make money sending traffic to ecommerce sites.

But later that year, Slide became a photo-sharing embeddable widget for MySpace and Facebook profiles.

Then, in 2008, Slide took $50 million in funding at a $500 million valuation. It began describing itself as an ad network built on top of a portfolio of widgets including hits like Top Friends and SuperPoke. During this era, Slide opened a New York sales office.

But by July 2009, Slide exited the business of selling standard ad units. The new plan, Slide VP Keith Rabois told us at the time, was to sell ” integrated sponsorships” for $500,000 to $1 million a pop. It shuttered its New York office.

Now, in 2010, Slide is a company that plans to make its money selling to users — and allowing users to sell — virtual goods. Max tells us virtual goods sales accounted for roughly 75% of Slide’s revenues in 2009. The goal is 90% by the end of 2010.

The new business seems to be going well — and not just for Slide. Making and selling virtual goods, one of its users made $16,000 in one month last year. (“That’s more than I make in a month,” volunteered Keith.) Slide hopes to build a business on attracting more of these types of “power users.”

In a world where Microsoft, Apple, Netscape and AOL all began life as something very different than the companies they would become — AOL sold on-demand video game consoles, you may recall — Slide’s ever-changing strategies are not sign of failure, but a sign that Max and his team are willing to keep evolving until they get it right.

Remember, going back to the drawing board paid off handsomely for Max the last time around.

Before it became the company and service we know it as today, PayPal was actually two companies: a Palm Pilot payments and cryptography company founded by Max, called Confiinity, and a financial services company called X.com. They merged in 2000, went public in 2002 and sold to eBay for $1.5 billion in the same year.

Last time we were in San Francisco, we toured an office full of people who hope Max can pull off that kind of trick again.